1. Field of the Invention
The present invention relates to a document retrieval apparatus which retrieves and displays a document on the basis of a retrieval keyword, and more particularly to a technique which visually clarifies the degree of relevance between a document and a retrieval keyword.
2. Background Art
It has been performed to retrieve desired documents on the basis of a retrieval keyword designated by a user, from a database in which a large number of documents are accumulated, Web sites which lie on a network, or the like.
In such a document retrieval, when those positions in the retrieved documents at which one or more retrieval keywords utilized for the retrieval are used are known, the necessities of the retrieved documents are easily judged on the basis of the retrieval keywords in the retrieved documents.
In order to cope with such a requirement, there has been put into practical use a method wherein the retrieval keywords are highlighted and displayed in the retrieved documents so as to become conspicuous.
Besides, in the document retrieval, it has been performed to retrieve documents by using similar words obtained by the thesaurus expansion of retrieval keywords. When it is known if the original retrieval keywords are contained in the documents thus retrieved using the similar words, or which of the retrieval keywords has been expanded to the individual similar words, conveniently a ground for the retrieval of each retrieved document can be clarified.
In this regard, in the document retrieval performing the thesaurus expansion of a retrieval keyword, there has been proposed an invention wherein the retrieval keyword and thesaurus-expanded similar words are highlighted and displayed at different densities in a retrieved document, in conformity with the degrees of similarity between the retrieval keyword and the similar words (refer to JP-A-11-250077).
Besides, there has been proposed an invention wherein similar words are highlighted and displayed in retrieved documents, and wherein retrieval keywords are denoted in small sizes under the similar words in order to clarify which of the retrieval keywords the similar words have been expanded from (refer to JP-A-11-73420).